Babe almost breaking into silly expression (8)

I believe the answer is:

locution

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'expression' is the definition.
(synonyms)

I cannot understand how the rest of the clue works.

(Other definitions for locution that I've seen before include "Style of speaking" , "Mode of expression" , "utterance" , "Phase or style of speech" , "Person's style of speech" .)

I've seen this clue in The Times.

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